Roller leveler and metal sheet flattening method

ABSTRACT

A roller leveler for flattening a metal sheet or plate having a cut-sheet form includes leveling rolls disposed in a staggered state on upper and lower sides of a pass line and configured to sandwich and flatten the metal sheet while pressing it therethrough, a hydraulic pressing cylinder for pressing the metal sheet via the leveling rolls, intermediate rolls set in contact with the respective leveling rolls from outside and larger in diameter than the leveling rolls, and a drive unit for rotating the intermediate rolls. The roller leveler causes the drive unit to rotate the intermediate rolls and transmits the driving force to the leveling rolls to pass the metal sheet while causing the pressing cylinder to press the metal sheet via the leveling rolls.

TECHNICAL FIELD

The present invention relates to a roller leveler for flattening a metalsheet or plate having a cut-sheet form and a metal sheet flatteningmethod.

BACKGROUND ART

In the process of manufacturing a metal sheet, such as a steel sheet,the metal sheet is subjected to rolling and cooling steps, in which themetal sheet undergoes deformation, such as warping and/or waving.Accordingly, in order to remedy the deformation, such as warping and/orwaving, and thereby to flatten the metal sheet, a roller leveler, whichincludes a plurality of leveling rolls disposed on upper and lower sidesin a staggered state, is used (for example, Patent Document 1).

The roller leveler is configured to pass a metal sheet to be flattenedbetween the lower rolls and the upper rolls, while pushing the upperrolls toward the lower rolls or pushing the lower rolls toward the upperrolls, to repeatedly apply bending to the metal sheet, and thereby toplanarize the warping and/or waving of the metal sheet. At this time,the pressing amount of the respective rolls of the roller leveler issuitably set to bend the metal sheet at a yield ratio preferably of 0.7or more.

PRIOR ART DOCUMENT Patent Document

Patent Document 1

Jpn. Pat. Appln. KOKAI Publication No. 2009-255148

SUMMARY OF INVENTION

When a conventional roller leveler is used to flatten a metal sheethaving a cut-sheet form, the driving force for passing the metal sheetdepends on the torque of the leveling rolls. In order to flatten a thinmetal sheet made of a material with a larger yield stress, the diameterof the rolls needs to be small. This brings about a problem such that,if it is arranged to ensure the yield ratio necessary for theflattening, the torque of the leveling rolls becomes insufficient topass the metal sheet.

This is because, in order to apply a sufficient pressing amount, driveshafts connected to drive the leveling rolls need to have a diametersmaller than that of the rolls. For this reason, when the leveling rollshave a small diameter to flatten a thin metal sheet, which is made of amaterial with a larger yield stress, their torque inevitably becomessmall. In this case, the torque may be smaller than the value necessaryfor passing the metal sheet if it is arranged to ensure the yield rationecessary for flattening the metal sheet.

In light of this problem, conventionally, when flattening is performedon a metal sheet having a small thickness and a large yield stress, itis necessary to restrictively set the pressing amount of the levelingrolls to a value that enables the sheet passing even by the torque ofthe leveling rolls. Consequently, there may be a case where the metalsheet is not sufficiently flattened.

The present invention has been made under the circumstances, and anobject of the present invention is to provide a roller leveler and ametal sheet flattening method, which can sufficiently flatten a metalsheet having a small thickness and a large yield stress.

In order to solve the problem mentioned above, the present inventionincludes the following aspects.

According to a first aspect of the present invention, there is provideda roller leveler for flattening a metal sheet having a cut-sheet form,the roller leveler including: a plurality of leveling rolls disposed ina staggered state on upper and lower sides of a pass line of the metalsheet to be flattened and configured to rotate to sandwich and flattenthe metal sheet while passing the metal sheet therethrough; a hydraulicpressing cylinder configured to press the metal sheet via the levelingrolls; a plurality of intermediate rolls disposed outside the pluralityof leveling rolls on the upper and lower sides and set in contact withthe respective leveling rolls from outside, the intermediate rollshaving a diameter larger than that of the leveling rolls; and a driveunit configured to rotate the intermediate rolls, wherein the rollerleveler is configured to cause the drive unit to drive the intermediaterolls for rotation and cause a driving force therefrom to be transmittedto the leveling rolls to pass the metal sheet while causing the pressingcylinder to press the metal sheet via the leveling rolls.

According to a second aspect of the present invention, there is provideda roller leveler including: a plurality of leveling rolls disposed in astaggered state on upper and lower sides of a pass line of a metal sheetto be flattened and configured to rotate to sandwich and flatten themetal sheet while passing the metal sheet therethrough; a plurality ofintermediate rolls disposed outside the plurality of leveling rolls onthe upper and lower sides and set in contact with the respectiveleveling rolls from outside, the intermediate rolls having a diameterlarger than that of the leveling rolls; a pair of roll frames thatsupport the leveling rolls and the intermediate rolls on the upper andlower sides, respectively; a pair of frames that support the pair ofroll frames on the upper and lower sides, respectively; a hydraulicpressing cylinder configured to press one of the pair of frames to pressthe metal sheet via one of the roll frames, the intermediate rolls, andthe leveling rolls; a drive unit configured to rotate the intermediaterolls; a plurality of hydraulic crowning cylinders arrayed in a widthdirection perpendicular to a pass direction of the metal sheet betweenone of the frames configured to be pressed by the pressing cylinder anda corresponding one of the roll frames; and a control system configuredto control flattening of the metal sheet, wherein the control system isconfigured to perform control to cause the drive unit to drive theintermediate rolls for rotation and cause a driving force therefrom tobe transmitted to the leveling rolls while causing the pressing cylinderto press the metal sheet via the leveling rolls, with the metal sheetbeing passed between the leveling rolls on the upper and lower sides,and wherein the control system is configured to obtain lateraldeflection amounts of the pair of frames, to calculate necessarytightening amounts of the respective hydraulic crowning cylindersnecessary for compensating for the deflection amounts, and to controltightening of the respective hydraulic crowning cylinders based on thenecessary tightening amounts.

In the second aspect, it is preferable that the control system beconfigured to calculate necessary tightening amounts of the respectivehydraulic crowning cylinders necessary for compensating for compressivedeformation of the pressing cylinder, the hydraulic crowning cylinders,the pair of roll frames, the intermediate rolls, and the leveling rollsbased on information on the compressive deformation, and to controltightening of the respective hydraulic crowning cylinders based on atotal value of the necessary tightening amounts necessary forcompensating for the compressive deformation and the necessarytightening amounts necessary for compensating for the deflection amountsof the pair of frames.

In the first and second aspects, it is preferable that the intermediaterolls have a diameter 1.2 to 2 times as large as a diameter of theleveling rolls, and the leveling rolls have a pitch, on each of theupper and lower sides, 1.2 to 2 times as large as the diameter of theleveling rolls. Further, it is preferable that the intermediate rolls beconfigured to be individually driven.

According to a third aspect of the present invention, there is provideda metal sheet flattening method of flattening a metal sheet having acut-sheet form in a roller leveler, which includes a plurality ofleveling rolls disposed in a staggered state on upper and lower sides ofa pass line of the metal sheet to be flattened and configured to rotateto sandwich and flatten the metal sheet while passing the metal sheettherethrough, a hydraulic pressing cylinder configured to press themetal sheet via the leveling rolls, a plurality of intermediate rollsdisposed outside the plurality of leveling rolls on the upper and lowersides and set in contact with the respective leveling rolls fromoutside, the intermediate rolls having a diameter larger than that ofthe leveling rolls, and a drive unit configured to rotate theintermediate rolls, the method including: inserting the metal sheetbetween the leveling rolls on the upper and lower sides; causing thepressing cylinder to press the metal sheet via the leveling rolls; andcausing the drive unit to drive the intermediate rolls for rotation andcausing a driving force therefrom to be transmitted to the levelingrolls to pass the metal sheet.

According to a fourth aspect of the present invention, there is provideda metal sheet flattening method of flattening a metal sheet having acut-sheet form by use of a roller leveler, which includes a plurality ofleveling rolls disposed in a staggered state on upper and lower sides ofa pass line of the metal sheet to be flattened and configured to rotateto sandwich and flatten the metal sheet while passing the metal sheettherethrough, a plurality of intermediate rolls disposed outside theplurality of leveling rolls on the upper and lower sides and set incontact with the respective leveling rolls from outside, theintermediate rolls having a diameter larger than that of the levelingrolls, a pair of roll frames that support the leveling rolls and theintermediate rolls on the upper and lower sides, respectively, a pair offrames that support the pair of roll frames on the upper and lowersides, respectively, a hydraulic pressing cylinder configured to pressone of the pair of frames to press the metal sheet via one of the rollframes, the intermediate rolls, and the leveling rolls, a drive unitconfigured to rotate the intermediate rolls, and a plurality ofhydraulic crowning cylinders arrayed in a width direction perpendicularto a pass direction of the metal sheet between one of the framesconfigured to be pressed by the pressing cylinder and a correspondingone of the roll frames, the method including: inserting the metal sheetbetween the leveling rolls on the upper and lower sides; causing thepressing cylinder to press the metal sheet via the leveling rolls; andcausing the drive unit to drive the intermediate rolls for rotation andcausing a driving force therefrom to be transmitted to the levelingrolls to pass the metal sheet; and obtaining lateral deflection amountsof the pair of frames; calculating necessary tightening amounts of therespective hydraulic crowning cylinders necessary for compensating forthe deflection amounts; and controlling tightening of the respectivehydraulic crowning cylinders based on the necessary tightening amounts.

In the fourth aspect, it is preferable that the method includecalculating necessary tightening amounts of the respective hydrauliccrowning cylinders necessary for compensating for compressivedeformation of the pressing cylinder, the hydraulic crowning cylinders,the pair of roll frames, the intermediate rolls, and the leveling rollsbased on information on the compressive deformation; and controllingtightening of the respective hydraulic crowning cylinders based on atotal value of the necessary tightening amounts necessary forcompensating for the compressive deformation and the necessarytightening amounts necessary for compensating for the deflection amountsof the pair of frames.

In the third and fourth aspects, it is preferable that the intermediaterolls have a diameter 1.2 to 2 times as large as a diameter of theleveling rolls, and the leveling rolls have a pitch, on each of theupper and lower sides, 1.2 to 2 times as large as the diameter of theleveling rolls. Further, it is preferable that the intermediate rolls beconfigured to be individually driven.

In the first to fourth aspects, it is preferable that a penetrationdepth to the metal sheet be reduced until a leading end of the metalsheet passes through an area where the leveling rolls are disposed, andthen is set at a value necessary for flattening the metal sheet afterthe leading end of the metal sheet passes through the area where theleveling rolls are disposed.

In the present invention, it is preferable that the metal sheet to beflattened be a steel sheet having a thickness of 2.0 to 25.4 mm and ayield stress of 400 to 1,800 MPa.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a roller leveler according to anembodiment of the present invention.

FIG. 2 is a front view showing the roller leveler according to theembodiment of the present invention.

FIG. 3 is a diagram for explaining the principle of the presentinvention.

FIG. 4 is a diagram, where the abscissa axis denotes the sheet thicknessand the ordinate axis denotes the yield stress, showing a flattenableregion, in which flattening can be performed at a yield ratio of 70%(0.7), respectively obtained in the case of the leveling rolls beingused alone and in the case of the leveling rolls being used along with adrawing operation by pinch rolls.

EMBODIMENT FRO CARRYING OUT THE INVENTION

An embodiment of the present invention will now be described withreference to the accompanying drawings.

FIG. 1 is a side view showing a roller leveler according to anembodiment of the present invention. FIG. 2 is a front view showing theroller leveler. The roller leveler 100 according to this embodiment isdesigned to flatten a metal sheet having a cut-sheet form, and includesa housing 1, an upper frame 2 disposed inside the housing 1, and a lowerframe 3 disposed to support the housing 1, as shown in the drawings.Hydraulic pressing cylinders (which may be referred to as “pushingcylinders”) 4 are disposed between the housing 1 and the upper frame 2,and an upper roll frame 5 is disposed below the upper frame 2 and ishung by an upper roll grip cylinder (not shown). A plurality of upperintermediate rolls 13 and upper leveling rolls 6 are disposed below theupper roll frame 5 and supported by the upper roll frame 5. The upperintermediate rolls 13 and the upper leveling rolls 6 are each formed ofa long body extending in the width direction, and the upper intermediaterolls 13 are set in contact with the upper side of the upper levelingrolls 6. A plurality of upper backup rolls 7 are disposed between therespective upper intermediate rolls 1.3 and the upper roll frame 5 toback up the upper intermediate rolls 13. The upper backup rolls 7 areeach formed of a short body and supported by the upper roll frame 5along the axial direction of the upper intermediate rolls 13.Accordingly, the pressing cylinders 4 press down the upper roll frame 5,the upper backup rolls 7, the upper intermediate rolls 13, and the upperleveling rolls 6.

In this specification, the term “press down” is intended to include notonly a case where the pressure is applied downward as shown in FIG. 1but also a case where the pressure is applied upward as explained laterin a modification. In other words, the term “press down” can be replacedwith the term “press” in this specification.

On the side opposite to the upper leveling rolls 6 with respect to thepass line of the metal sheet P, a plurality of lower leveling rolls 8are disposed and a plurality of lower intermediate rolls 14 are disposedbelow the lower leveling rolls 8. The lower leveling rolls 8 and thelower intermediate rolls 14 are supported by a lower roll frame 10disposed therebelow. The lower leveling rolls 8 and the lowerintermediate rolls 14 are each formed of a long body extending in thewidth direction, and the lower intermediate rolls 14 are set in contactwith the lower side of the lower leveling rolls 8. A plurality of lowerbackup rolls 9, each being formed of a short body, are disposed alongthe axial direction of the lower intermediate rolls 14 between therespective lower intermediate rolls 14 and the lower roll frame 10 toback up the lower intermediate rolls 14 and are supported by the lowerroll frame 10. The lower roll frame 10 is disposed on the lower frame 3.In place of the pressing cylinders 4 for pressing the upper levelingrolls 6, pressing cylinders for pressing the lower leveling rolls 8 maybe used.

The upper intermediate rolls 13 and the lower intermediate rolls 14 havea diameter larger than the diameter of the upper leveling rolls 6 andthe lower leveling rolls 8. The diameter of the upper intermediate rolls13 and the lower intermediate rolls 14 is set preferably at 1.2 to 2.0times, and more preferably at 1.4 to 2.0 times, as large as the diameterof the upper leveling rolls 6 and the lower leveling rolls 8. The pitchof the plurality of upper leveling rolls 6 and the plurality of lowerleveling rolls E is set preferably at 1.2 to 2.0 times, and morepreferably at 1.4 to 2.0 times, as large as the diameter of the upperleveling rolls 6 and the lower leveling rolls 8, as in the case of thediameter of the upper intermediate rolls 13 and the lower intermediaterolls 14. This pitch is equal to or larger than the conventional pitch,because the corresponding pitch according to the conventional rollerlevelers is set at 1.02 to 1.2 times the diameter of the leveling rolls.If the pitch of the leveling rolls is larger than 2.0 times the diameterof the leveling rolls, the sets of leveling rolls on the opposite sidesbite into each other, thereby hindering the yield ratio from increasing.

The upper intermediate rolls 13 and the lower intermediate rolls 14 arerespectively provided with drive units 15 (FIGS. 1 and 2 show only oneunit for the sake of convenience) each including a rotary motor, so thatthe upper intermediate rolls 13 and the lower intermediate rolls 14 arerotated by the drive units 15. The driving force of the drive units 15is transmitted to the upper leveling rolls 6 and the lower levelingrolls 8 to pass the metal sheet P between the upper leveling rolls 6 andthe lower leveling rolls 8, while pressing the metal sheet P by thepressing cylinders 4 via the upper leveling rolls 6 to flatten the metalsheet P.

The upper frame 2 and the upper roll frame 5 are coupled with each otherby a plurality of hydraulic crowning cylinders 12 disposed therebetween.As shown in FIG. 2, the respective crowning cylinders 12 are disposed atregular intervals to correspond to the leveling rolls 6 and 8 in thewidth direction perpendicular to the pass direction of the metal sheetP. As shown in FIG. 1, the hydraulic crowning cylinders 12 are arrayedin two rows. Although the crowning cylinders may be disposed in a row,the crowning cylinders disposed in two rows make it possible to morefinely correct the local lateral deflection of the upper roll frame 5.The hydraulic crowning cylinders 12 are each equipped with a positiondetection sensor (not shown) built therein. The hydraulic crowningcylinders may be disposed between the lower roll frame 10 and the lowerframe 3, or they may be disposed on both of the upper and lower sides.

As shown in FIG. 2, deflection detection sensors 21 are disposed atpositions central in the horizontal direction above the upper frame 2and configured to detect the lateral deflection of the upper frame 2. Asshown in FIG. 1, the deflection detection sensors 21 are two sensorsarranged along the pass line of the metal sheet P. The deflectiondetection sensors 21 continuously detect the distances to the lower sideof the upper frame 2 to calculate the deflection amount of the upperframe 2 based on the distances. Further, deflection detection sensors 22are disposed in internal space of the lower frame 3. The deflectiondetection sensors 22 are two sensors arranged, at positions central inthe lateral direction, along the pass line of the metal sheet P. Thedeflection detection sensors 22 continuously detect the distances to theupper side of the lower frame 3 to calculate the deflection amount ofthe lower frame 3 based on the distances. The configuration describedabove may be modified such that only one of the upper frame 2 and thelower frame 3 is provided with deflection detection sensors and thedeflection amount of the other frame is calculated using proportion.

Load cells (or hydraulic pressure converters) 23 are attached betweenthe pressing cylinders 4 and the housing 1, and used to detectcompressive deformation of the pressing cylinders 4, hydraulic crowningcylinders 12, upper roll frame 5, upper backup rolls 7, upperintermediate rolls 13, upper leveling rolls 6, lower leveling rolls 8,lower intermediate rolls 14, lower backup rolls 9, and lower roll frame10.

The roller leveler 100 according to this embodiment is designed suchthat a control system 50 controls its respective components. The controlsystem 50 includes a process controller having a CPU, a user interfaceconnected to the process controller and having a keyboard and a display,and a storage section that stores recipes containing control programs(software) and process condition data recorded therein.

A required recipe is retrieved from the storage section and executed bythe process controller in accordance with an instruction or the likeinput through the user interface. Consequently, the roller leveler 100can perform a predetermined process (operational sequence) as describedlater under the control of the process controller. The recipescontaining control programs and process condition data that are storedin a computer readable storage medium, such as a magnetic disk (flexibledisk, hard disk, etc.), an optical disk (CD, DVD, etc.), amagneto-optical disk (MO, etc.), and/or a semiconductor memory, may beused.

Alternatively, the recipes may be available online, that is, may betransmitted from another apparatus through, e.g., a dedicated line, asneeded.

In order to flatten the metal sheet P (i.e., to perform leveling), thecontrol system 50 controls the penetration depth (pressing amount) ofthe leveling rolls 6 given by the pressing cylinders 4 and the drivingof the intermediate rolls 13 and 14 made by the drive units 15. Further,the control system 50 receives information on the deflection of theupper frame 2 and the lower frame 3 sent thereto from the deflectiondetection sensors 21 and 22, or it receives, in addition to thisinformation, information on the compressive deformation of the pressingcylinders 4, hydraulic crowning cylinders 12, upper roll frame 5, upperbackup rolls 7, upper intermediate rolls 13, upper leveling rolls 6,lower leveling rolls 8, lower intermediate rolls 14, lower backup rolls9, and lower roll frame 10 sent thereto. Then, the control system 50uses its calculating function to calculate necessary tightening amountsof the respective hydraulic crowning cylinders 12 based on the pieces ofinformation mentioned above, so that it controls the tightening by therespective hydraulic crowning cylinders 12 based on positionalinformation obtained by the position detection sensors in the respectivehydraulic crowning cylinders 12.

Next, an explanation will be given of an operation of the roller leveler100 thus structured, in flattening a metal sheet P having a cut-sheetform.

When the leveling rolls 6 and 8 are used to reduce the internal stressof the metal sheet P by their driving force and flatten the metal sheetP, it is necessary to satisfy the following formula (1), where, inassociation with the metal sheet P, “t” (mm) is sheet thickness, E(N/mm²) is Young's modulus, δy (N/mm²) is yield stress, D (mm) is rolldiameter, and n is yield ratio.

1−n=(δy.D)/(E.t)  (1)

In this formula, the yield ratio is required to be 0.7 or more tosufficiently reduce the internal stress. Accordingly, it is necessary tosatisfy the following formula (2).

0.3 ≧(δy.D)/(E.t)  (2)

This formula can be transformed into the following formula (3).

D ≦0.3(E.t)/E.t)/δy  (3)

Accordingly, it is necessary that the smaller the sheet thickness “t” isor the larger the yield stress δy is, the smaller the diameter of theleveling rolls is set. However, the smaller the diameter of the levelingrolls is, the smaller the torque of the leveling rolls becomes.

Accordingly, when the leveling rolls are used to flatten a metal sheethaving a small thickness and a large yield stress and are given apenetration depth (pressing amount) to obtain a yield ratio necessaryfor flattening the metal sheet, the material to be flattened, it maybecome difficult to pass the metal sheet because of an insufficienttorque of the leveling rolls.

According to this embodiment made in light of this problem, the upperintermediate rolls 13 and the lower intermediate rolls 14 arerespectively disposed above the upper leveling rolls 6 and below thelower leveling rolls 8 and they have a diameter larger than that of theleveling rolls 6 and 8. The upper intermediate rolls 13 and the lowerintermediate rolls 14 are individually rotated by the drive mechanisms15 to transmit the rotation to the upper leveling rolls 6 and the lowerleveling rolls 8. The driving force thus transmitted is used to pass themetal sheet P between the upper leveling rolls 6 and the lower levelingrolls 8, while pressing the metal sheet P by the pressing cylinders 4,to flatten the metal sheet P. Consequently, the driving force forpassing the metal sheet P increases and thereby makes it possible topass the metal sheet while applying the pressing amount necessary forthe flattening, even when the metal sheet has a small thickness and alarge yield stress.

Next, this will be specifically explained.

FIG. 3 is a diagram for explaining the principles of an increase in thedriving force that occurs when the intermediate rolls have a largerdiameter. In the case where the leveling rolls are driven, thetangential force F₁ corresponding to the driving force for passing themetal sheet P is expressed by F₁=T/D, where D is the diameter of theleveling rolls and T is the torque of leveling rolls. On the other hand,in the case where the intermediate rolls having a larger diameter aredriven and the driving force is transmitted to the leveling rolls, andthe diameter of the intermediate rolls is twice as large as that of theleveling rolls or it is defined as 2D, the torque of the intermediaterolls is expressed by 8T because the torque is proportional to the cubicof the diameter. At this time, the tangential force F₂ corresponding tothe force transmitted from the intermediate rolls to the leveling rollsis expressed by F₂=8T/2D, and thus F₂ is four times as large as F₁. Thetangential force F₂ thus transmitted to the leveling rolls becomes thedriving force for passing the metal sheet P. Accordingly, when theintermediate rolls doubled in diameter is driven and the driving forceis transmitted to the leveling rolls, the sheet passing force for themetal sheet P increases fourfold. In the case where the diameter of theintermediate rolls is 1.2 times the diameter of the leveling rolls, thisrenders F₂=1.2³T/1.2D, which is 1.44 times as large as F₁, so that thesheet passing force for the metal sheet P increases 1.44 fold. In thisway, the intermediate rolls having a larger diameter are disposed anddriven to transmit the driving force to the leveling rolls, so that thedriving force for passing the metal sheet P increases and thereby makesit possible to pass the metal sheet while applying the pressing amountnecessary for the flattening, even when the metal sheet has a smallthickness and a large yield stress.

In this case, as described above, the diameter of the upper intermediaterolls 13 and the lower intermediate rolls 14 is set preferably at 1.2 to2.0 times, and more preferably at 1.4 to 2.0 times, as large as thediameter of the upper leveling rolls 6 and the lower leveling rolls 8.The pitch of the plurality of upper leveling rolls 6 and the pluralityof lower leveling rolls 8 is set preferably at 1.2 to 2.0 times, andmore preferably at 1.4 to 2.0 times, as large as the diameter of theupper leveling rolls 6 and the lower leveling rolls 8, as in the case ofthe diameter of the upper intermediate rolls 13 and the lowerintermediate rolls 14. However, when the pitch of the leveling rolls isincreased in this way, an increase in the penetration depth to the metalsheet P makes it difficult to pass the metal sheet P. In light of thisproblem, it is preferable to set the penetration depth smaller to passthe metal sheet P until the leading end of the metal sheet P passesthrough the area where the leveling rolls are disposed, that is, theleveling roll array area, and then to set the penetration depth at therequired value to flatten the metal sheet P after the leading end of themetal sheet P passes through the leveling roll array area.

According to this embodiment, the flattening of the metal sheet P can beperformed by a single passing of the metal sheet P through the levelingroll array area. However, as described above, there may be a case wherethe penetration depth is reduced to pass the metal sheet P until theleading end of the metal sheet P passes through the leveling roll arrayarea. In such a case, in order to compensate for insufficient flatteningat the portion including the leading end of the metal sheet P, it ispreferable to pass the metal sheet P back and forth once or more throughthe leveling roll array area.

When the metal sheet used is a steel sheet, the technique according tothis embodiment can be suitably used to process the steel sheet having athickness of 2.0 to 25.4 mm and a yield stress of 400 to 1,800 MPa,which has been difficult to flatten.

FIG. 4 is a diagram, where the abscissa axis denotes the sheet thicknessand the ordinate axis denotes the yield stress, showing the region(flattenable region), in which flattening can be performed at a yieldratio of 70% (0.7), respectively obtained in the case where the levelingrolls are driven and in the case where the intermediate rolls having alarger diameter are driven and the driving force is transmitted to theleveling rolls according to this embodiment. As shown in FIG. 4, use ofthe intermediate rolls having a larger diameter provides a remarkablyexpanded flattenable region, so that it is possible to flatten amaterial having a relatively small thickness of 12.7 mm or less and alarge yield stress of 1,200 MPa or more, to obtain a metal sheet withhigh flatness. The relationship shown in FIG. 4 is obtained when theleveling rolls having a diameter of 135 mm are used to performflattening.

As described above, by driving the intermediate rolls having a largerdiameter, it is possible to flatten the metal sheet, the material to beflattened, with the required penetration depth (pressing amount) toattain high flatness. In this case, however, some of the components ofthe machine, such as the upper frame 2 and the lower frame 3, may bedeflected in the width direction and, when this occurs, the penetrationdepth to the metal sheet varies in the width direction because of thedeflection. Accordingly, in this embodiment, when it is desired toeliminate the influence of the deflection, detection values obtained bythe deflection detection sensors 21 and/or 22 are used to derive thedeflection amounts of the upper frame 2 and the lower frame 3. Then, thenecessary tightening amounts of the respective hydraulic crowningcylinders 12 are calculated to compensate for the deflection amounts,and are used to perform a crowning correction on the upper levelingrolls 6. Consequently, it is possible to reduce the difference in thepenetration depth in the width direction of the metal sheet P, thematerial to be flattened, which makes it possible to perform theflattening with higher flatness.

In addition to the necessary tightening amounts of the respectivehydraulic crowning cylinders 12 necessary for compensating for thedeflection amounts of the upper frame 2 and the lower frame 3, thenecessary tightening amounts of the respective hydraulic crowningcylinders 12 for compensating for the compressive deformation may becalculated based on the information on compressive deformation obtainedvia the load cells (or hydraulic pressure converters) 23 attachedbetween the pressing cylinders 4 and the housing 1, that is, theinformation on compressive deformation of the pressing cylinders 4,hydraulic crowning cylinders 12, upper roll frame 5, upper backup rolls7, upper intermediate rolls 13, upper leveling rolls 6, lower levelingrolls 8, lower intermediate rolls 14, lower backup rolls 9, and lowerroll frame 10, and the total value of the two sets of the necessarytightening amounts may be used to perform a crowning correction on theupper leveling rolls 6. This makes it possible to further reduce thedifference in the penetration depth in the width direction of the metalsheet P, the material to be flattened, making it possible to perform theflattening with much higher flatness.

Japanese Patents No. 3443036 and No. 3726146 disclose crowningcorrection of this type in detail, the entire contents of which areincorporated by reference herein.

According to this embodiment of the present invention, intermediaterolls having a diameter larger than that of leveling rolls are disposedso as to be in contact with the leveling rolls from outside. A drivingforce is applied to the intermediate rolls to transmit the driving forceto the leveling rolls, thereby passing a metal sheet between theleveling rolls. In this case, the driving force for passing the metalsheet can be increased. Consequently, even when the metal sheet has asmall thickness and a large yield stress, it is possible to pass themetal sheet while applying a penetration depth necessary for theflattening, which improves the flatness of the metal sheet. Further, inaddition to this, by performing the crowning correction in the widthdirection, it is possible to further improve the flatness of the metalsheet.

The present invention is not limited to the embodiment described above,and it may be modified in various manners. For example, in theembodiment described above, the machine has a structure designed topress (press downward) the upper rolls of the leveling rolls toward thelower rolls, but it may be modified to press (press upward) the lowerrolls toward the upper rolls. Further, the present invention should beconstrued to encompass arrangements obtained by omitting some of thecomponents of the embodiment described above, as long as they do notdepart from the scope of the present invention.

1. A roller leveler for flattening a metal sheet having a cut-sheetform, the roller leveler comprising: a plurality of leveling rollsdisposed in a staggered state on upper and lower sides of a pass line ofthe metal sheet to be flattened and configured to rotate to sandwich andflatten the metal sheet while passing the metal sheet therethrough; ahydraulic pressing cylinder configured to press the metal sheet via theleveling rolls; a plurality of intermediate rolls disposed outside theplurality of leveling rolls on the upper and lower sides and set incontact with the respective leveling rolls from outside, theintermediate rolls having a diameter larger than that of the levelingrolls; and a drive unit configured to rotate the intermediate rolls,wherein the roller leveler is configured to cause the drive unit todrive the intermediate rolls for rotation and cause a driving forcetherefrom to be transmitted to the leveling rolls to pass the metalsheet while causing the pressing cylinder to press the metal sheet viathe leveling rolls.
 2. The roller leveler according to claim 1, furthercomprising: a pair of roll frames that support the leveling rolls andthe intermediate rolls on the upper and lower sides, respectively,wherein one of the pair of frames is configured to be pressed by thepressing cylinder from a side opposite to the leveling rolls; aplurality of hydraulic crowning cylinders arrayed in a width directionperpendicular to a pass direction of the metal sheet between one of theframes configured to be pressed by the pressing cylinder and acorresponding one of the roll frames; and a control system configured tocontrol flattening of the metal sheet, wherein the control system isconfigured to perform control to cause the drive unit to drive theintermediate rolls for rotation and cause a driving force therefrom tobe transmitted to the leveling rolls while causing the pressing cylinderto press the metal sheet via the leveling rolls, with the metal sheetbeing passed between the leveling rolls on the upper and lower sides,and wherein the control system is configured to obtain lateraldeflection amounts of the pair of frames, to calculate necessarytightening amounts of the respective hydraulic crowning cylindersnecessary for compensating for the deflection amounts, and to controltightening of the respective hydraulic crowning cylinders based on thenecessary tightening amounts.
 3. The roller leveler according to claim2, wherein the control system is configured to calculate necessarytightening amounts of the respective hydraulic crowning cylindersnecessary for compensating for compressive deformation of the pressingcylinder, the hydraulic crowning cylinders, the pair of roll frames, theintermediate rolls, and the leveling rolls based on information on thecompressive deformation, and to control tightening of the respectivehydraulic crowning cylinders based on a total value of the necessarytightening amounts necessary for compensating for the compressivedeformation and the necessary tightening amounts necessary forcompensating for the deflection amounts of the pair of frames.
 4. Theroller leveler according to claim 1, wherein the intermediate rolls havea diameter 1.2 to 2 times as large as a diameter of the leveling rolls,and the leveling rolls have a pitch, on each of the upper and lowersides, 1.2 to 2 times as large as the diameter of the leveling rolls. 5.The roller leveler according to claim 1, wherein the intermediate rollsare configured to be individually driven.
 6. The roller leveleraccording to claim 1, wherein a pressing amount to the metal sheet isreduced until a leading end of the metal sheet passes through an areawhere the leveling rolls are disposed, and then is set at a valuenecessary for flattening the metal sheet after the leading end of themetal sheet passes through the area where the leveling rolls aredisposed.
 7. The roller leveler according to claim 1, wherein the metalsheet to be flattened is a steel sheet having a thickness of 2.0 to 25.4mm and a yield stress of 400 to 1,800 MPa.
 8. A metal sheet flatteningmethod of flattening a metal sheet having a cut-sheet form in a rollerleveler, which includes a plurality of leveling rolls disposed in astaggered state on upper and lower sides of a pass line of the metalsheet to be flattened and configured to rotate to sandwich and flattenthe metal sheet while passing the metal sheet therethrough, a hydraulicpressing cylinder configured to press the metal sheet via the levelingrolls, a plurality of intermediate rolls disposed outside the pluralityof leveling rolls on the upper and lower sides and set in contact withthe respective leveling rolls from outside, the intermediate rollshaving a diameter larger than that of the leveling rolls, and a driveunit configured to rotate the intermediate rolls, the method comprising:inserting the metal sheet between the leveling rolls on the upper andlower sides; causing the pressing cylinder to press the metal sheet viathe leveling rolls; and causing the drive unit to drive the intermediaterolls for rotation and causing a driving force therefrom to betransmitted to the leveling rolls to pass the metal sheet.
 9. The metalsheet flattening method which according to claim 8, wherein the rollerleveler further includes a pair of roll frames that support the levelingrolls and the intermediate rolls on the upper and lower sides,respectively, a pair of frames that support the pair of roll frames onthe upper and lower sides, respectively, wherein one of the pair offrames is configured to be pressed by the pressing cylinder from a sideopposite to the leveling rolls, metal sheet via one of the roll frames,the intermediate rolls, and the leveling rolls, a plurality of hydrauliccrowning cylinders arrayed in a width direction perpendicular to a passdirection of the metal sheet between one of the frames configured to bepressed by the pressing cylinder and a corresponding one of the rollframes, the method further comprising: obtaining lateral deflectionamounts of the pair of frames; calculating necessary tightening amountsof the respective hydraulic crowning cylinders necessary forcompensating for the deflection amounts; and controlling tightening ofthe respective hydraulic crowning cylinders based on the necessarytightening amounts.
 10. The metal sheet flattening method according toclaim 9, wherein the method comprises calculating necessary tighteningamounts of the respective hydraulic crowning cylinders necessary forcompensating for compressive deformation of the pressing cylinder, thehydraulic crowning cylinders, the pair of roll frames, the intermediaterolls, and the leveling rolls based on information on the compressivedeformation; and controlling tightening of the respective hydrauliccrowning cylinders based on a total value of the necessary tighteningamounts necessary for compensating for the compressive deformation andthe necessary tightening amounts necessary for compensating for thedeflection amounts of the pair of frames.
 11. The metal sheet flatteningmethod according to claim 8, wherein the intermediate rolls have adiameter 1.2 to 2 times as large as a diameter of the leveling rolls,and the leveling rolls have a pitch, on each of the upper and lowersides, 1.2 to 2 times as large as the diameter of the leveling rolls.12. The metal sheet flattening method according to claim 8, wherein theintermediate rolls are configured to be individually driven.
 13. Themetal sheet flattening method according to claim 8, wherein a pressingamount to the metal sheet is reduced until a leading end of the metalsheet passes through an area where the leveling rolls are disposed, andthen is set at a value necessary for flattening the metal sheet afterthe leading end of the metal sheet passes through the area where theleveling rolls are disposed.
 14. The metal sheet flattening methodaccording to claim 8, wherein the metal sheet to be flattened is a steelsheet having a thickness of 2.0 to 25.4 mm and a yield stress of 400 to1,800 MPa.
 15. The roller leveler according to claim 1, furthercomprising a plurality of backup rolls that back up the plurality ofintermediate rolls on the upper and lower sides.
 16. The metal sheetflattening method according to claim 8, wherein the roller levelerfurther includes a plurality of backup rolls that back up the pluralityof intermediate rolls on the upper and lower sides.